Bioreactor for treating sewage and sewage treatment system comprising the same

ABSTRACT

Disclosed is a bioreactor for treating sewage comprising an aerobic tank including a mixing cell for receiving sewage to be supplied from an inlet and mixing the sewage with activated sludge and an aerobic reactor tank in which the activated sludge adsorbs organic substance existing in the sewage; a backwashing cartridge filter for removing floc resulting from growth of the activated sludge adsorbing the organic substance; and an anaerobic tank for carrying out a denitrification process for denitrifying treated water flowed through the backwashing cartridge filter using anaerobic ammonium oxidation (anammox) bacteria wherein the backwashing cartridge filter allows the sewage discharged from the aerobic tank to pass through the cartridge filter and separates the floc and the treated water using difference in size between the floc contained in the sewage and pores in the cartridge filter, and wherein foreign matter adsorbed on the cartridge filter is easily removed by means of washing water to be injected into the cartridge filter.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to a bioreactor for treating sewage and asewage treatment system comprising the same and more particularly, to abioreactor and a sewage treatment system comprising the bioreactor,which have a simple structure, are excellent in treatment efficiency,and are utilized in treating sewage, food wastes, or livestock wastes.

Description of the Related Art

Conventional sewage treatment facilities often utilize a standardactivated sludge process or a process to which the above process isadded or in which the above process is modified. Further, in somecountries, A2/O process, UCT process, VIP process, or the like are usedin the sewage treatment facilities. The processes used in thosecountries as mentioned above are not applicable to a confluent typesewage exclusion system in other countries. The A2/O process is aprocess for removing nitrogen and phosphorus, in which an A/O process isimproved with a biological treatment process wherein a reactor comprisesan anaerobic tank, anoxic tank and an aerobic tank and is configured tocarry out a nitrified recycle process for removing nitrate nitrogen anda process for returning activated sludge from a clarifier. The anaerobictank serves to release phosphorus under anaerobic conditions such thatmicroorganisms can ingest nutritions excessively in the aerobic tank.The anaerobic tank serves to remove nitrogen and phosphorus bydenitrifying nitrate in the internal return water of the aerobic tank.

The A2/O process removes nitrogen and phosphorus in sewage to reducenutrients in the sewage. However, this process has problems in that itfocuses on only removal of nitrogen and phosphorus in the sewage, butbacteria and microorganisms in the sewage, which recently come to thefront as being harmful to the human body, may not be removed in theprocess.

Almost majority of conventional sewage treatment plants are operatedthrough a biological treatment method using a way of decomposingcontaminants by microorganisms. The biological treatment method has beenproved for a long time as having good performance and being the mosteffective and safe method. However, it has a problem in that surplussludge may occur.

Most surplus sludge causes a treatment problem because it is organicsubstance that is microbial mass and hence easy to decay. Heretofore,treatment of the surplus sludge has mainly relied on marine dumping andpartly on reclamation or incineration. The amount of surplus sludgegenerated as of 2012 is more than 10,000 tons per day, which becomesmore than 3.65 million tons of sludge per year. The surplus sludge isexpected to increase continually in the future.

As a treatment for the surplus sludge, marine dumping has been bannedsince 2012, and a policy for promotion of conversion of organic wastesinto new and renewable energy, such as conversion of wastes intoresources and energy and reduction of wastes, has been carried out.Particularly, in the sludge treatment by means of an anaerobic digestiontank, a pre-treatment process for solubilization is carried out in orderto increase treatment efficiency. Examples of the pre-treatmenttechnology include a biological approach using thermophilic aerobicmicroorganisms, a physical approach using ultrasonic waves, hydrodynamiccavitation, thermal hydrolysis, or a ball mill apparatus, a chemicalapproach using ozone treatment and alkali chemical treatment, a combinedtreatment approach in which a plurality of treatment methods asmentioned are combined, and an electric approach using electrolysis.However, these approaches have a problem in that costs therefor are highor reduction efficiency is low, and thus it is difficult to put them topractical use.

Korean Patent No. 10-135458 discloses a method of solubilizing sludgefor increasing digestion efficiency of an anaerobic digestion tank,where surplus sludge generated in the process of treating wastewater istreated with alkali catalyst and methanol to soften or destroy cellmembranes of biodegradable microorganisms in the sludge so that theanaerobic digestion efficiency can be enhanced by anaerobicmicroorganisms in the digestion tank.

SUMMARY OF THE DISCLOSURE

It is an object of the present disclosure to provide a bioreactor fortreating sewage which is of a simple structure so that plottage areatherefor can be minimized and which is excellent in solid-liquidseparation efficiency after agglomeration of organic substance so thatthe amount of sludge generated and the time of treatment are reduced.

It is another object of the present disclosure is to provide a sewagetreatment system comprising a bioreactor according to the presentdisclosure, which is capable of reducing the amount of by-productgenerated and the treatment time while minimizing the plottage area forthe system through the simple structure of the bioreactor and which iscapable of producing and recovering biogas.

Other objects and advantages of the present disclosure will be moreapparent from the following detailed description of the disclosure,claims and drawings.

Embodiments of the present disclosure are provided to explain thepresent disclosure more fully to those skilled in the art. Theembodiments described below may be modified into various other forms andthe scope of the present disclosure is not limited to the embodimentsdescribed below. Rather, these embodiments are provided to make thisdisclosure thorough and complete and fully convey the spirit of thepresent disclosure to those skilled in the art.

In the drawings, thickness or size of each layer are assumed forconvenience and clarity of description and the same reference numeralsare used to refer to the same components. The term “and/or” as usedherein includes all combinations of any one or one or more of itemslisted in the corresponding sentence.

Terms as used herein are intended to describe a specific embodiment butnot limit the present disclosure. As used herein, the singular form mayinclude the plural form unless the context clearly indicates otherwise.Also, terms “comprise” and/or “comprising” as used herein are intendedto specify the presence of configurations, integers, steps, operations,members, elements and/or groups thereof but not exclude the presence oraddition of one or more other configurations, integers, operations,members, elements and/or groups thereof.

In accordance one aspect of the present disclosure, a bioreactor fortreating sewage comprises an aerobic tank including an inlet forsupplying sewage, a mixing cell for receiving the sewage and mixing thesewage with activated sludge, an aerobic reactor tank continuouslycoupled to the mixing cell, in which the activated sludge adsorbsorganic substance, and an outlet for discharging sewage containingorganic substance adsorbed on the activated sludge in the aerobicreactor tank; a backwashing cartridge filter for removing floc resultingfrom growth of the activated sludge adsorbing the organic substance fromthe sewage discharged through the outlet of the aerobic tank; and ananaerobic tank for carrying out a denitrification process fordenitrifying treated water having been passed through the backwashingcartridge filter, using anaerobic ammonium oxidation (anammox) bacteriawherein the backwashing cartridge filter allows the sewage dischargedfrom the aerobic tank to pass through the cartridge filter and separatesthe floc and the treated water, using difference in size between thefloc contained in the sewage and pores in the cartridge filter andwherein foreign matter adsorbed on the cartridge filter is easilyremoved by means of washing water to be injected into the cartridgefilter.

According to an embodiment of the present disclosure, the backwashingcartridge filter of the present disclosure may comprise a cartridgefilter housing; a cartridge filter fixedly installed inside thecartridge filter housing to separate the floc and the treated water; atransfer port arranged at an upper end of the cartridge filter to allowthe treated water having been passed through the cartridge filter to bedischarged therethrough; and an inlet arranged at a lower end of thecartridge filter to allow the washing water for removing the floc nothaving been passed through the cartridge filter to be introducedtherethrough. According to an embodiment of the present disclosure, thecartridge filter of the present disclosure may comprise a large numberof pores having a diameter of 50 to 150 μm.

According to an embodiment of the present disclosure, the backwashingcartridge filter of the present disclosure may further comprise a sludgesupply piping for transferring the separated floc to the aerobic tank.

According to an embodiment of the present disclosure, the activatedsludge of the present disclosure may comprise at least one selected fromthe group consisting of ammonia-oxidizing archaea (AOA),ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).

According to an embodiment of the present disclosure, the aerobicreactor tank of the present disclosure may further comprise an airinjection unit for injecting air.

In accordance with another aspect of the present disclosure, there isprovided a sewage treatment system comprising a primary sedimentationtank for sedimenting sewage containing sludge to separate the sewageinto raw sludge and settled sewage water; a bioreactor according toclaim 1 for allowing organic substance in the sewage separated in theprimary sedimentation tank to be adsorbed on activated sludge such thatthe organic substance is separated out of the sewage and carrying out adenitrification process; a secondary sedimentation tank for sedimentingsurplus sludge in the sewage having adsorbed the organic substance in anaerobic tank of the bioreactor; a dehydration tank for dehydrating theraw sludge recovered by being sedimented in the primary sedimentationtank and the surplus sludge recovered by being sedimented in thesecondary sedimentation tank; a digestion tank for anaerobicallydigesting the raw sludge and the surplus sludge dehydrated in thedehydration tank to produce biogas; and a sequential batch reactor (SBR)reaction tank for removing nitrogen by allowing supernatant containingammonium generated in the digestion tank to react with anaerobicammonium oxidation (anammox) bacteria.

According to an embodiment of the present disclosure, the bioreactor ofthe present disclosure may comprise a backwashing cartridge filter forremoving floc resulting from growth of the activated sludge adsorbingorganic substance.

According to an embodiment of the present disclosure, the backwashingcartridge filter of the present disclosure may comprise a cartridgefilter housing; a cartridge filter fixedly installed inside thecartridge filter housing to separate the floc and the treated water; atransfer port arranged at an upper end of the cartridge filter to allowthe treated water having been passed through the cartridge filter to bedischarged therethrough; and an inlet arranged at a lower end of thecartridge filter to allow the washing water for removing the floc nothaving been passed through the cartridge filter to be introducedthercthrough.

According to an embodiment of the present disclosure, the cartridgefilter of the present disclosure may comprise a large number of poreshaving a diameter of 50 to 150

According to an embodiment of the present disclosure, the activatedsludge of the present disclosure may comprise at least one selected fromthe group consisting of ammonia-oxidizing archaea (AOA),ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).

According to an embodiment of the present disclosure, the bioreactor ofthe present disclosure may further comprise an air injection unit forinjecting air to allow the organic substance in the sewage to beadsorbed on the activated sludge.

According to an embodiment of the present disclosure, the anaerobicammonium oxidation (anammox) bacteria of the present disclosure isPlanctomycetes.

According to an embodiment of the present disclosure, the anaerobicammonium oxidation (anammox) bacteria of the present disclosure isPlanctomycetes granules.

According to an embodiment of the present disclosure, the SBR reactiontank of the present disclosure may be connected to a treated waterreservoir and the treated water reservoir may comprise a backwashingcartridge filter for selectively separating the activated sludge.

According to an embodiment of the present disclosure, the sewagetreatment system may further comprise a biogas collector for collectingthe biogas generated in the digestion tank of the present disclosure.

In accordance with still another aspect of the present disclosure, thereis provided a method of treating sewage, comprising: 1) primarilysedimenting sewage containing sludge to separate the sewage into rawsludge and settled sewage water; 2) allowing organic substance in thesettled sewage water separated in the primarily sedimenting sewage to beadsorbed on activated sludge such that the organic substance isseparated out of the settled sewage water and carrying out adenitrification process; 3) subsequently to the step 2), secondarilysedimenting surplus sludge in the settled sewage water, on which theorganic substance have been adsorbed, to separate the surplus sludgefrom treated sewage water; 4) recovering and discharging the treatedsewage water from which the surplus sludge has been layer-separated bybeing sedimented in the secondarily sedimenting surplus sludge that isthe step 3); 5) dehydrating the raw sludge recovered by being sedimentedin the primarily sedimenting sewage that is the step 1) and the surplussludge recovered by being sedimented in the secondarily sedimentingsurplus sludge that is the step 3); 6) anaerobically digesting the rawsludge and the surplus sludge dehydrated in the step 5) to producebiogas; and 7) removing nitrogen by allowing supernatant containingammonium generated in the step 6) to react with anaerobic ammoniumoxidation (anammox) bacteria.

According to an embodiment of the present disclosure, the step 2) of thepresent disclosure is intended to allow the organic substance in thesettled sewage water to be adsorbed on the activated sludge such thatfloc resulting from growth of the activated sludge adsorbing the organicsubstance is separated wherein a backwashing cartridge filter may beutilized in order to separate the floc.

According to an embodiment of the present disclosure, the activatedsludge in the step 2) of the present disclosure may comprise at leastone selected from the group consisting of ammonia-oxidizing archaea(AOA), ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria(NOB).

According to an embodiment of the present disclosure, the anaerobicammonium oxidation (anammox) bacteria in the step 7) of the presentdisclosure is Planctomycetes.

According to the bioreactor for treating sewage that is provided in thepresent disclosure, since a large amount of organic substance containedin the sewage is cohered in organic substance cohesion bodies and thensolid-liquid separation is carried out with high efficiency by means ofa backwash cartridge filter, treatment time may be shortened. Inaddition, since the activated sludge separated is recycled, sludgedischarge amount may be significantly reduced. As a result, sewagetreatment efficiency per unit area of plottage may be further enhancedwhile minimizing the area of plottage.

Furthermore, since the backwashing cartridge filter is utilized, it ispossible to remove foreign matter adhered in the cartridge filter byinjecting washing water to the cartridge filter without need to performa separate washing process for removing the foreign matter adhered inthe cartridge filter so that replacement frequency of the cartridgefilter may be extended.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic view illustrating a structure of a bioreactor fortreating sewage according to an embodiment of the present disclosure;

FIG. 2 is a schematic view illustrating a structure of a backwashingcartridge filter according to an embodiment of the present disclosure;

FIG. 3 is a schematic view showing a flow in a bioreactor for treatingsewage comprising a backwashing cartridge filter according to anembodiment of the present disclosure;

FIG. 4 is a schematic view showing a flow at the time of backwashing ina bioreactor for treating sewage comprising a backwashing cartridgefilter according to an embodiment of the present disclosure; and

FIG. 5 is a schematic view illustrating a structure of a sewagetreatment system according to an embodiment of the present disclosure.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Preferred embodiments of the present disclosure will now be described.However, the embodiments of the present disclosure can be modified intovarious other forms and the scope of the present disclosure is notlimited to the embodiments described below. Further, the embodiments ofthe present disclosure are provided to explain the present disclosuremore fully to those skilled in the art.

A bioreactor for treating sewage and a sewage treatment system of thepresent disclosure will be described with reference to the drawings.

FIG. 1 schematically illustrates a structure of a bioreactor fortreating sewage according to an embodiment of the present disclosure. InFIG. 1, the bioreactor 20 comprises an aerobic tank 21 for allowingorganic substance contained in the sewage to be adsorbed on activatedsludge, a backwashing cartridge filter 24 for separating sludge on whichthe organic substance is adsorbed, and an anaerobic tank 25 for adenitrification process.

More specifically, the bioreactor 20 for treating sewage comprises theaerobic tank 21 including an inlet for supplying sewage, a mixing cell22 for receiving the sewage and mixing the sewage with activated sludge,the aerobic reactor tank 23 continuously coupled to the mixing cell 22,in which the activated sludge adsorbs organic substance, and an outletfor discharging sewage containing organic substance adsorbed on theactivated sludge in the aerobic reactor tank 23.

The bioreactor 20 additionally comprises the backwashing cartridgefilter 24 for separating sludge which has adsorbed the organic substancefrom the sewage discharged through the outlet of the aerobic tank, andthe anaerobic tank 25 for carrying out a denitrification process fordenitrifying the treated water, which has passed through the separationmembrane bioreactor (MBR), using anaerobic ammonium oxidation (anammox)bacteria.

In this embodiment of the present disclosure, the sewage to be treatedis supplied through the inlet of the bioreactor 20, and then theactivated sludge is mixed with the sewage. Then, the activated sludgereacts with the sewage so that the organic substance contained in thesewage is adsorbed on the activated sludge. The activated sludgecomprises at least one selected from the group consisting ofammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB) andnitrite-oxidizing bacteria (NOB), and adsorbs the organic substance.

Further, in this embodiment of the present disclosure, the mixing cell22 may further comprise at least one agitator to facilitate the processfor mixing the sewage and the activated sludge.

In this embodiment of the present disclosure, the agitator is notparticularly limited in its configuration but may be of an impeller typewith blades. In this case, the impeller type agitator is notparticularly limited. However, according to a preferred embodiment ofthe present disclosure, the impeller type agitator may be formed in amanner that an outer blade portion is bent a downward direction of aninner blade portion such that water is pushed out to the desireddirection. As a result, the agitator may collect and push out the waterstrongly, thereby maximizing agitation effect.

If the present disclosure adopts a plurality of agitators, blades of theplurality of agitators may have the same or different diameters.Preferably, arranging the plurality of agitators having different bladediameters such that the diameters are reduced gradually from an upperportion of a chamber to a lower portion of the chamber may make itpossible to maintain a much faster mixing speed while allowing inflowwater to flow from the upper portion to the lower portion of thechamber.

In this case, the number of revolutions (G-value) of the blade of theagitator is not particularly limited and may be appropriately selecteddepending on scale of mixing and agglomeration or size of the chamber.Preferably, it may be 30 to 110 sec⁻¹.

This embodiment of the present disclosure may further comprise an airinjection unit 26 of FIG. 5 at a lower end of the aerobic reactor tank23 so that adsorption of the organic substance contained in the sewageon the activated sludge in the aerobic reactor tank 23 can befacilitated.

Further, in this embodiment of the present disclosure, an auxiliaryagent may be further added together with the activated sludge, where theauxiliary agent may be selected from the group consisting of clay,calcium hydroxide, cation flocculant, anionic flocculant and non-ionflocculant.

In this embodiment of the present disclosure, when the organic substancecontained in the sewage as described above is grown into floc 110 in theaerobic reactor tank 23, the sewage treated as described above issupplied to the backwashing cartridge filter 24 connected to the aerobicreactor tank 23. The activated sludge on which the organic substancecontained in the sewage has been adsorbed cannot pass through thecartridge filter 100 within the backwashing cartridge filter 24, and mayremain as solid sludge. Accordingly, in this embodiment of the presentdisclosure, the sewage containing the floc 110 can be separated into thesolid sludge and liquid sewage primarily treated through the backwashingcartridge filter 24.

In this embodiment of the present disclosure, the backwashing cartridgefilter 24 comprises a cartridge filter housing 200, a cartridge filter100 fixedly installed inside the cartridge filter housing to separatethe sludge which has adsorbed the organic substance, a transfer port 300arranged at an upper end of the cartridge filter to allow the treatedwater having been passed through the cartridge filter to be dischargedtherethrough, and an inlet 400 arranged at a lower end of the cartridgefilter to allow the washing water for removing the sludge, which has not\passed through the cartridge filter, to be introduced therethrough.

In this embodiment of the present disclosure, the cartridge filter maycomprise a large number of pores having a diameter of 50 to 150 μm.Since the cartridge filter comprises a large number of fine-sized pores,the floc 110 having diameters exceeding 150 μm cannot pass through thecartridge filter, whereas only the treated water passes through thecartridge filter and is introduced into the cartridge filter. Theprimarily treated water introduced as mentioned above can be transferredto the anaerobic tank through the transfer port 300.

In this embodiment of the present disclosure, the backwashing cartridgefilter 24 may be configured to remove the floc 110 adhered to thecartridge filter by injecting washing water thereto. In a conventionalbioreactor in which the floe 110 is removed using a separation membrane,occlusion phenomenon of the membrane that foreign matter is adsorbed onthe separation membrane may occur. In order to prevent the occlusionphenomenon, it has been necessary to remove the foreign matter adheredto the separation membrane using an air injection unit, or to replacethe separation membrane with a new one. However, according to thepresent disclosure, since the backwashing cartridge filter 24 isutilized, it may be easy to remove the foreign matter adsorbed on thecartridge filter 24 by injecting the washing water through the inlet400, and it may be possible to recycle the removed foreign matter bytransferring it back to the aerobic tank 21. Further, it may beunnecessary to provide a separate air injection unit for cleaning theseparation membrane. For this reason, in comparison with theconventional separation membrane bioreactor, consumption of electricpower can be minimized and replacement cycle of the cartridge filter canbe extended so that usage time can be prolonged.

When foreign matter adsorbed to the cartridge filter is removed usingthe washing water, it is possible to contemplate using external washingwater. However, as shown in FIG. 4 of the present disclosure, it ispossible to use the primarily treated water passing through thecartridge filter 24 as washing water by injecting it through the inlet400.

In other words, since it is possible to use the primarily treated wateras washing water by regulating flow of the primarily treated water andtransferring it into the cartridge filter 24 through the inlet 400, noseparate washing water is required.

Therefore, in addition to the way of injecting separate washing waterinto the inlet 400 to remove foreign matter from the cartridge filter24, it is also possible to use the way of regulating flow of theprimarily treated water and then injecting the primarily treated waterthrough the inlet 400 to use it as washing water.

Since that no additional water is required when using the primarilytreated water as washing water, the treatment cost can be reduced.Further, cleaning of the cartridge filter 24 may be selectively carriedout depending on the degree of adsorption of foreign matter, thusenhancing production efficiency.

Further, in this embodiment of the present disclosure, the backwashingcartridge 24 may further comprise a sludge supply piping 130 fortransferring the separated sludge to the aerobic tank 21 so that theseparated solid sludge can be transferred back to the aerobic tank 21.

FIG. 2 schematically illustrates structure of a backwashing cartridgefilter according to an embodiment of the present disclosure. The sewagewater treated in the aerobic tank 21 contains floc resulting from growthof the activated sludge adsorbing organic substance. In order to treatthis floc 110, the floe is forced to pass through the cartridge filter100. Due to the point that diameters of pores of the cartridge filterare smaller than the size of the floc 100, the floc 110 cannot passthrough the cartridge filter and thus it is separated. The separatedfloc 110 remain outside the cartridge filter while the treated waterflowed through the cartridge filter is transferred to the anaerobic tank25, so that the sewage treatment process proceeds.

When the sewage treatment process is repeatedly carried out, the outersurface of the cartridge filter 100 is in a state that a large number ofthe floc 110 is adsorbed thereto. In this regard, occulusion phenomenonof the cartridge filter 100 of the present disclosure may also occurlike the conventional separation membrane bioreactor. In order toprevent this problem, the backwashing cartridge filter 24 of the presentdisclosure further comprises the inlet 400 for introducing wash waterinto it. The washing water is injected through the inlet 400 and forcedto pass through the cartridge filter from inside to outside of thecartridge filter. At this time, as the washing water passes through thecartridge filter from inside to outside of the cartridge filter, thefloc 110 adsorbed on the outside of the membrane can be removed by thewashing water. In other words, the floc 110 can be separated and removedin accordance with flow direction of the treated water and the washingwater 130 passing through the cartridge filter. The floc 110 separatedby the washing water 130 will remain inside the cartridge filter housing200 and will be recovered and transferred back to the aerobic tank 21for reuse.

As shown in FIG. 5, the sewage is treated in a primary sedimentationtank 10 where raw sludge is settled and liquid sewage is separated, andthen the separated sewage water is transferred to the bioreactor 20where processes of removal of organic substance and denitrification arccarried out by forcing the separated sewage water to pass through theaerobic tank 21, the separation membrane bioreactor 24, and theanaerobic tank 25 in the bioreactor 20.

The bioreactor 20 is same as that shown in FIG. 1 and thus detaileddescription thereof is omitted herein.

The secondarily treated water from which nitrogen has been removed inthe anaerobic tank 25 stays in a secondary sedimentation tank 30 wheresurplus sludge is settled, removed, and then discharged after passingthrough a disinfection process.

The raw sludge and the surplus sludge which are settled and separated inthe primary and secondary sedimentation tanks are transferred to adehydration tank 40 where they are subjected to a dehydration process.The concentrated sludge after the dehydration process is transferred toa digestion tank 50.

In the digestion tank 50 of this embodiment of the present disclosure,the surplus sludge and the raw sludge may be subjected to an anaerobicdigestion process using anaerobic microorganisms.

Here, the anaerobic digestion process is also referred to as “methanefermentation.” It is a series of processes for converting organicsubstance contained in the surplus sludge into methane by decompositionof various anaerobic microorganisms. More specifically, the anaerobicdigestion process proceeds by passing through a process of liquefyingsolid organic substance and hydrolyzing it, a process of generatinglower grade fatty acid (e.g., volatile organic acid: VFA) that generatesvinegar acid, propionic acid and butyric acid, a process of decomposingthe lower grade fatty acid into vinegar acid and H₂ gas and a process ofgenerating methane using those products.

The digestion tank 50 of the present disclosure makes it possible torecover energy in the form of biogas such as methane simultaneously withtreatment of the concentrated sludge. Therefore, in this embodiment ofthe present disclosure, the system may further comprise a biogascollector (not shown) for collecting biogas generated in the digestiontank 50 and, if necessary, further comprise a biogas separation membranefor separating methane and carbon dioxide contained in biogas.

In the present disclosure, when the anaerobic digestion process iscarried out in the digestion tank 50, digested sludge and supernatantthat cannot be recycled any more are generated. The digested sludge maybe discarded, whereas the supernatant may be supplied to an SBR reactiontank 60.

The SBR reaction tank 60 refers to a sequential batch reactor whichutilizes a continuous batch type activated sludge process. In theconventional SBR process, functions of a reaction tank and a secondaryclarifier are provided in a single batch tank and processes for reactionand sedimentation of the mixed solution, drainage of supernatant waterand discharge of the settled sludge are repeatedly carried out.

In the case of the conventional sewage treatment system, after theanaerobic digestion process is carried out using the concentrated sludgein the digestion tank 50, the generated supernatant liquid istransferred back to the primary sedimentation tank where it isreprocessed. However, in this case, since the supernatant liquidgenerated in the digestion tank 50 contains NH⁴⁺ or NO²⁻, if the sewagetreatment is carried out in the continuous process, concentration ofnitrogen increases continuously and thus concentration of C (carbon)/N(Nitrogen) exceeds 1 in the bioreactor 20, which ultimately causes aproblem that energy production efficiency in the digestion tank 50 islowered significantly.

In the present disclosure, in order to prevent the above mentionedproblem, the supernatant liquid generated in the digestion tank 50 istransferred to the SBR reaction tank 60 to react with anaerobic ammoniumoxidation (Anammox) bacteria so that NH⁴⁺ and NO²⁻ contained in thesupernatant liquid are converted into N₂ and then nitrogen can beremoved.

In this embodiment of the present disclosure, the anaerobic ammoniumoxidation bacteria may be Planctomycetes. In general, AOB bacteria usedas the activated sludge in the bioreactor 20 can convert about 50% ofNH⁴⁺ into NO²⁻, but Planctomycetes used in the SBR reaction tank 60 ofthe present disclosure can convert whole of NH⁴⁺ and NO²⁻ into N₂.Further, in the present disclosure, the Planctomycetes are adsorbed tothe surrounding organic substance and, as a result of that, floc (orgranule) is formed where the floc can be selectively separated dependingits particle size in the backwashing cartridge filter 62, as describedbelow, since particle size of the floc may be relatively large comparedto AOA, AOB and NOB bacteria.

In the present disclosure, although the sewage treatment process iscarried out by transferring to the primary sedimentation tank 10 thefinal treated water generated in the SBR reaction tank 60 after nitrogencontained in the supernatant liquid in the SBR reaction tank 60 isremoved as described above, energy production efficiency can bemaintained even in a continuous process for sewage treatment since ratioof. C/N in the bioreactor 20 can be maintained at less than or equal to1.

Reference is now made to FIG. 5 which schematically illustratesstructure of a sewage treatment system according to an embodiment of thepresent disclosure. Specifically, the SBR reaction tank 60 in thisembodiment of the present disclosure comprises a treatment tank 61 and abackwashing cartridge filter 62.

In this embodiment of the present disclosure, the supernatant liquidtransferred to the SBR reaction tank 60 may be contained in thetreatment tank 61. In addition, in this embodiment of the presentdisclosure, the backwashing cartridge filter 62 comprises a cartridgefilter and a detailed description thereof is omitted because it is thesame as that provided with reference to FIGS. 2 to 4.

In the present disclosure, the supernatant liquid transferred to thetreatment tank 61 is anaerobically digested by the anaerobic ammoniumoxidation bacteria and, as a result of that, floc is formed.

In the present disclosure, since a large number of pores included in thecartridge filter are controlled to have a diameter of 50 to 150 μm, thefloc cannot pass through a separation membrane module, whereas bacteriasuch as AOA, AOB and NOB in the activated sludge within the bioreactor20 can again pass through the cartridge filter.

Further, in the present disclosure, the supernatant liquid purified asabove and bacteria such as AOA, AOB, and NOB contained therein may beseparately recovered and supplied back to the primary sedimentation tank10 through a treated water feedback piping 64.

More specifically, anaerobic digestion reaction of the supernatantliquid by the anaerobic ammonium oxidation bacteria occurs in thetreatment tank 61 of the SBR reaction tank 60, the supernatant liquidpurified by the anaerobic digestion reaction is transferred to a treatedwater reservoir 63, and then the bacteria such as AOA, AOB and NOB andthe floc generated by the anaerobic ammonium oxidation bacteria can beseparated using the backwashing cartridge filter 62. In other words, thefloe cannot pass through the cartridge filter of the backwashingcartridge filter 62, whereas bacteria such as AOA, AOB and NOB againpass through the cartridge filter, the purified supernatant liquidcontaining the bacteria, having been passed through the cartridgefilter, is supplied back to the primary sedimentation tank 10 throughthe treated water feedback piping 64, and the flock is transferred tothe treatment tank 61 of the SBR reaction tank 60 through a floctransfer piping 65.

The present disclosure has been described in detail with reference tospecific embodiments. The embodiments are provided by way of exampleonly in order to facilitate understanding of the present disclosure, butthe scope of the present disclosure should not be limited thereto.

1-19. (canceled)
 20. A bioreactor for treating sewage comprising: anaerobic tank configured to receive sewage, mix the sewage with activatedsludge, adsorb organic substance existing in the sewage on the activatedsludge, and discharge sewage containing organic substance adsorbed onthe activated sludge; a device configured to separate sludge on whichthe organic substance is adsorbed from the sewage discharged from theaerobic tank; and an anaerobic tank configured to carry out adenitrification process for denitrifying treated water using anaerobicammonium oxidation (anammox) bacteria.
 21. The bioreactor according toclaim 1, wherein the device is a backwashing cartridge filter configuredto remove floc resulting from growth of the activated sludge adsorbingthe organic substance.
 22. The bioreactor according to claim 2, whereinthe backwashing cartridge filter passes the sewage discharged from theaerobic tank through the cartridge filter and separates the floc and thetreated water using difference in size between the floc contained in thesewage and pores in the cartridge filter.
 23. The bioreactor accordingto claim 1, wherein the aerobic tank comprises: an inlet configured tosupply the sewage; a mixing cell configured to receive the sewage andmix the sewage with the activated sludge; an aerobic reactor tankcoupled to the mixing cell, in which the activated sludge adsorbs theorganic substance; and an outlet configured to discharge sewagecontaining organic substance adsorbed on the activated sludge in theaerobic reactor tank.
 24. The bioreactor according to claim 4, whereinthe mixing cell comprises at least one agitator to facilitate theprocess for mixing the sewage and the activated sludge.
 25. Thebioreactor according to claim 5, wherein the agitator is of an impellertype with blades configured to be formed in a manner that an outer bladeportion is bent a downward direction of an inner blade portion such thatwater is pushed out to a desired direction.
 26. The bioreactor accordingto claim 6, wherein the mixing cell comprises a plurality of agitatorshaving different blade diameters and arranges the plurality of agitatorshaving different blade diameters such that diameters are reducedgradually from an upper portion of the mixing cell to a lower portion ofthe mixing cell.
 27. The bioreactor according to claim 3, wherein thebackwashing cartridge filter comprises: a cartridge filter housing; acartridge filter fixedly installed inside the cartridge filter housingto separate the floc and the treated water; a transfer port arranged atan upper or lower end of the cartridge filter to allow the treated waterflowed through the cartridge filter to be discharged therethrough; andan inlet arranged at an upper or lower end of the cartridge filter toallow the washing water for removing the floc not having been passedthrough the cartridge filter to be introduced therethrough.
 28. Thebioreactor according to claim 8, wherein the backwashing cartridgefilter comprises a large number of pores having a diameter of 50 to 150μm.
 29. The bioreactor according to claim 8, wherein the backwashingcartridge filter further comprises a sludge supply piping configured totransfer the separated floc to the aerobic tank.
 30. The bioreactoraccording to claim 1, wherein the activated sludge comprises oneselected from the group consisting of ammonia-oxidizing archaea (AOA),ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).31. The bioreactor according to claim 11, wherein an auxiliary agent isadded together with the activated sludge, the auxiliary agent beingselected from the group consisting of clay, calcium hydroxide, cationflocculant, anionic flocculant and non-ion flocculant.
 32. Thebioreactor according to claim 4, wherein the aerobic reactor tankfurther comprises an air injector configured to inject air to allow theorganic substance in the sewage water to be adsorbed on the activatedsludge.
 33. The bioreactor according to claim 1, wherein the device is aseparation membrane bioreactor (MBR) configured to separate theactivated sludge adsorbing the organic substance from the sewagedischarged from the aerobic tank.
 34. A sewage treatment systemcomprising: a primary sedimentation tank configured to sediment sewagecontaining sludge to separate the sewage into raw sludge and settledsewage water; a bioreactor comprising: an aerobic tank configured toreceive sewage supplied from an inlet, mix the sewage with activatedsludge in a mixing cell, adsorb organic substance existing in the sewageon the activated sludge in an aerobic reactor tank, and discharge sewagecontaining organic substance adsorbed on the activated sludge through anoutlet; a device configured to separate sludge on which the organicsubstance is adsorbed from the sewage discharged from the aerobic tank;and an anaerobic tank configured to carry out a denitrification processfor denitrifying treated water using anaerobic ammonium oxidation(anammox) bacteria, wherein the bioreactor adsorbs organic substance inthe settled sewage water separated in the primary sedimentation tank onthe activated sludge such that the organic substance is separated out ofthe settled sewage water and carries out the denitrification process; asecondary sedimentation tank configured to sediment surplus sludge inthe settled sewage water, on which the organic substance has adsorbed inthe aerobic tank of the bioreactor; a dehydration tank configured todehydrate the raw sludge recovered by being sedimented in the primarysedimentation tank and the surplus sludge recovered by being sedimentedin the secondary sedimentation tank; a digestion tank configured toanaerobically digest the raw sludge and the surplus sludge dehydrated inthe dehydration tank to produce biogas; and a sequential batch reactor(SBR) reaction tank configured to remove nitrogen by allowingsupernatant containing ammonium generated in the digestion tank to reactwith anaerobic ammonium oxidation (anammox) bacteria.
 35. The sewagetreatment system according to claim 15, wherein the device of thebioreactor is a backwashing cartridge filter configured to remove flocresulting from growth of the activated sludge adsorbing the organicsubstance, and wherein the backwashing cartridge filter comprises: acartridge filter housing; a cartridge filter fixedly installed insidethe cartridge filter housing to separate the floc and the treated water;a transfer port arranged at an upper or lower end of the cartridgefilter to allow the treated water having been passed through thecartridge filter to be discharged therethrough; and an inlet arranged ata lower or upper end of the cartridge filter to allow the washing waterfor removing the floc not having been passed through the cartridgefilter to be introduced therethrough.
 36. The sewage treatment systemaccording to claim 16, wherein the activated sludge comprises oneselected from the group consisting of ammonia-oxidizing archaea (AOA),ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).37. The sewage treatment system according to claim 16, wherein theanaerobic ammonium oxidation (anammox) bacteria is Planctomycetes(Brocadia, Kuenenia, Anammoxoglobus, Jettenia and Scalindua includingheterotrophic bacteria).
 38. The sewage treatment system according toclaim 15, wherein the SBR reaction tank is connected to a treated waterreservoir, and the treated water reservoir comprises a backwashingcartridge filter configured to selectively separate the activatedsludge.
 39. The sewage treatment system according to claim 15, furthercomprising a biogas collector for collecting the biogas generated in thedigestion tank.